Most of conventional chair cushions and bed mattresses include a cover or case into which a whole piece of sponge, foamed rubber or other similar elastic material stuffed. Such conventional cushions and/or mattresses prevent users from directly contacting with the rigid chairs and/or beds, so that the users may comfortably sit or lie on the chairs or the beds. A disadvantage of such conventional cushions and mattresses stuffed with sponge or foamed rubber is they have poor air permeability. A patient lying on bed with such conventional cushion or mattress for a prolonged time will suffer from skin problems, such as bedsore.
An inflatable cushion 30 shown in FIG. 10 has been developed in an attempt to overcome the above-mentioned disadvantage of the conventional stuffed cushions. The inflatable cushion 30 mainly includes a bottom wall 32 made of rubber material, and an integrally formed air cushion having a plurality of communicable air cells 34. Air filled in the air cells 34 provides a suitable air pressure inside the air cushion to allow the same to bear the weight of a user sitting or lying on the cushion. Such inflatable cushion 30 has better air permeability than the conventional stuffed cushions to advantageously avoid undesirable bedsore or other skin problems.
U.S. Pat. No. 5,502,855 discloses a zoned cellular cushion that has a series of separately inflatable zones with tubular conduits leading from each zone beneath or on top of the cushion within the periphery of the cushion to a common manifold spaced outwardly from the front edge of the cushion with a fill tube connected to the manifold and individual cut-off valves or a means to buckle the tubes for each conduit, whereby the zones can be filled and bled simultaneously or selectively.
U.S. Pat. No. 5,369,828 discloses an inflatable cushion with upstanding pyramidal air cells. The inflatable cushion disclosed in this patent includes a flexible bottom wall and a plurality of upstanding air cells having flexible generally vertical side walls. The air cells is substantially pyramidal in shape and has a substantially rectangular flexible lower section defined by the vertical side walls and sealed to the bottom wall, and a flexible domed tapered top area connected to the vertical side walls. The side walls of adjacent cells are separated and spaced apart to define lateral and longitudinal paths and are independently upstanding when inflated. And there are tubing connected to the air cells through the bottom wall to adjust and monitor the air pressure in the cells from beneath the cushion.
Following are some drawbacks existing in the above-described conventional inflatable cushion 30:
1. The air cells 34 of the inflatable cushion 30 are integrally formed onto a top of the bottom wall 32. Separate molds are required to manufacture inflatable cushions 30 having different sizes and different numbers of air cells 34 and therefore largely increase the manufacturing cost of such inflatable cushion 30.
2. The conventional inflatable cushion 30 is integrally molded. However, molds for forming the inflatable cushion 30 have limitations in their sizes. Therefore, it is not possible to manufacture an inflatable cushion 30 having a considerably large area, such as a cushion for use as a bed mattress. That is, the inflatable cushion 30 has only limited usage, such as a chair cushion having small area.
3. A finished inflatable cushion 30 has fixed dimensions and unchangeable arrangement of the air cells 34 on the bottom wall 32. Moreover, since the air cells 34 are communicable with one another, the inflatable cushion 30 is not foldable to change its size for use on a smaller chair or wheelchair. In other words, an inflatable cushion 30 can only be used on a chair seat having a size similar to or larger than that of the bottom wall 32 of the inflatable cushion 30.
4. Although the inflatable cushion 30 may prevent a patient lying thereon from bedsore, it does not help a patient who has already suffered from bedsore and/or other illnesses in connection with, for example, the backbone. In a worse condition, the inflatable cushion 30 might even cause worsened bedsore and/or spine disease. The time and occasion suitable for using the inflatable cushion 30 is therefore limited, too.
5. Since the air cells 34 are communicable with one another, any leak on any of the air cells 34 shall make the whole inflatable cushion 30 useless and undesirably shortens the usable life of the inflatable cushion 30.